This invention is directed to building products, particularly novel window, door frames, and the like, and to such products being made by extruding certain thermoplastic resins. The structure may be a co-extruded profile of at least two thermoplastic resins such as a vinyl aromatic polymer composition and an ultra violet light (UV) and weather resistance coating thereover. It may also be a single extruded polymer profile.
There is prior art with respect to a window assembly of a rigid plastic material employing polyvinyl chloride. U.S. Pat. No. 4,831,781 is directed to such a material for window jamb and head members which may be hollow. U.S. Pat. No. 4,516,356 is directed to an insulated plastic frame for doors, windows and the like wherein the window and door frames are made of extruded plastic. The extruded plastic structure employs polyvinyl chloride and the hollow sections of the plastic structure are filled with an insulating material such as a foamed material. U.S. Pat. No. 4,130,976 is directed to frames for doors, windows and the like consisting of a hollow metal profile within a foamed synthetic resin profile. The outer portion of the synthetic resin profile is a densified resin outer skin. U.S. Pat. No. 3,964,231 is directed to a plastic-encased metallic hollow profile member. The profile consists of a metallic hollow profile member having a plastic sheath extruded thereover. None of these references, however, disclose or suggest the unique structure of the present invention or the advantages achieved thereby, as well as the particular thermoplastics employed herein.
In today's market, thermoplastic polymers, particularly polyvinyl-chloride (vinyl), have found extensive use in door and window frame construction and in siding. However, vinyls have a problem in that they are not very resistant to the extreme heats of the southerly and westerly sections of the United States of America, or the hot climates in other parts of the world. White pigmented vinyls are particularly used in such warm climates, but even they will fail in that they can crack or deform due to heat build-up. Dark pigmented vinyls are even worse with respect to heat resistance or heat build-up. In addition, to obtain rigidity (stiffness), thicker walled sections have been made. However, even heavier walled vinyls still suffer from heat build-up and can crack or deform, although to a lesser degree because of the heavier walled sections. Hollow metal profile with vinyl coverings are used as shown in the above art.
The heat build-up that occurs in the hot weather is in the infrared spectrum. The heat build-up causes shrinkage of the vinyl parts, thereby resulting in breakage, softening and/or deformation where the vinyl parts are in a restrained mode, such as a window or door frame. What probably occurs is that as the heat builds up, temperatures of the vinyl can exceed its glass transition temperature (Tg). When the temperature of the vinyl goes above its Tg, the stresses developed in the vinyl during extrusion are relieved, thereby causing it to shrink. When the vinyl shrinks, it may crack or warp, if the vinyl profile or frame is restrained.